DECKGL integration - Phase 1 (#3771)

* DECKGL integration

Adding a new set of geospatial visualizations building on top of the
awesome deck.gl library. https://github.com/uber/deck.gl

While the end goal it to expose all types of layers and let users bind
their data to control most props exposed by the deck.gl API, this
PR focusses on a first set of visualizations and props:

* ScatterLayer
* HexagonLayer
* GridLayer
* ScreenGridLayer

* Addressing comments

* lint

* Linting

* Addressing chri's comments

superset/assets/javascripts/explore/components/controls/SelectControl.jsx

@@ -17,6 +17,7 @@ const propTypes = {
   multi: PropTypes.bool,
   name: PropTypes.string.isRequired,
   onChange: PropTypes.func,
+  onFocus: PropTypes.func,
   value: PropTypes.oneOfType([PropTypes.string, PropTypes.number, PropTypes.array]),
   showHeader: PropTypes.bool,
   optionRenderer: PropTypes.func,
@@ -34,6 +35,7 @@ const defaultProps = {
   label: null,
   multi: false,
   onChange: () => {},
+  onFocus: () => {},
   showHeader: true,
   optionRenderer: opt => opt.label,
   valueRenderer: opt => opt.label,
@@ -115,6 +117,7 @@ export default class SelectControl extends React.PureComponent {
       clearable: this.props.clearable,
       isLoading: this.props.isLoading,
       onChange: this.onChange,
+      onFocus: this.props.onFocus,
       optionRenderer: VirtualizedRendererWrap(this.props.optionRenderer),
       valueRenderer: this.props.valueRenderer,
       selectComponent: this.props.freeForm ? Creatable : Select,